1. Field of the Invention
The present invention relates to an ultrasonic motor using ultrasonic vibration generated by its ultrasonic vibrator for driving energy.
2. Description of the Prior Art
In conventional ultrasonic motors, there were devised various means for effectively converting the driving energy from the ultrasonic vibrator into kinetic energy for the movable member. For example, a retaining member for retaining the ultrasonic vibrator is installed at a position in agreement with the node of the ultrasonic vibration so that the retaining member is kept from generating vibration and the driving energy is prevented from dissipating to the outside through the housing.
In such an arrangement as described above, however, there is a problem that a vibration is generated in the retaining member when a load is connected to the motor or when the load is varied, and thereby, the driving energy is dissipated to the outside. The reason a vibration is generated in the retaining member when a load is connected to the motor is that, when the ultrasonic vibrator is pressed against the movable member and load is connected to the motor, then, even if the retaining member has been set up at a nominal position in agreement with the node of the vibration in the initial stage where no load was connected to the motor, deformation or other changes occur in the component parts by action of the press exerted on the movable member or variations in the load, and, due to uncertain factors such as the deformation, the position of the node of the vibration is moved from the position where the retaining member is installed. When a vibration is thus generated in the retaining member, such problems arise that output efficiency of the motor is lowered due to the fact that the operation of the motor becomes unstable or the driving energy is consumed by the vibration of the retaining member, or undesirable effects might occur due to the fact that the vibration is propagated through the housing to external equipment.